A BIOSENSOR BASED ON THE MEMBRANE-PROTEIN LACTOSE PERMEASE

We are attempting to develop biosensors based on membrane proteins. The prototype which will be presented is based on the transport protein lactose permease, which occurs in the inner membrane of the bacterium Escherichia coli. The protein catalyses the transport of lactose through the membrane in a strict 1:1 stoichiometry with protons. A lipid membrane containing lactose permease is spread onto a glass surface and a pH-sensitive fluorescent dye is entrapped in the space between the lipid membrane and the glass surface. When the external concentration of lactose is altered, lactose molecules together with protons are transported into this space and the protons are detected by a change in fluorescence intensity. This change is related to the change in the exterior lactose concentration. The conditions for a good sensor function have been worked out.